Blown film tube collapsing

ABSTRACT

A blown film tube collapsing frame comprising two separate plenum chambers having perforate metal surfaces facing a blown film, tube, or bubble is used to force air through the perforations in said surfaces to collapse the tube or bubble. Each plenum chamber contains adjustable baffles, movable by ropes to fit any size bubble, to ensure the air egress through the perforations immediately adjacent the bubble. Magnets imbeded into the surface of the baffles ensure contact of the perforated plate and the baffles.

United States Patent [1 1 Robinson BLOWN FILM TUBE COLLAPSING [75]Inventor: Leroy E. Robinson, Bartlesville,

Okla.

[73] Assignee: Phillips Petroleum Company,

Bartlesville, Okla.

[22] Filed: Mar. 20, 1972 [2]] Appl. No.: 236,112

Related US. Application Data [62] Division of Scr. No. 08,977, Feb. 5,l970, Pat. No.

[52] US. Cl. 425/387, 425/326 [51] Int. Cl. 329d 7/00 [58] Field ofSearch 239/562, 563, 564;

[56] References Cited UNlTED STATES PATENTS 3,700,763 lO/l972 VanKralingen 425/326 X Jan.8,1974

2/1971 Denniniger et a1. 239/563 X 9/l930 Carrington 239/563 X PrimaryExaminerM. Henson Wood, Jr. Assistant Examiner-Andres KashnikowAtt0rneyYoung & Quigg [57] ABSTRACT A blown film tube collapsing framecomprising two separate plenum chambers having perforate metal surfacesfacing a blown film, tube, or bubble is used to force air through theperforations in said surfaces to collapse the tube or bubble. Eachplenum chamber contains adjustable baffles, movable by ropes to fit anysize bubble, to ensure the air egress through the perforationsimmediately adjacent the bubble. Magnets imbeded into the surface of thebaffles ensure contact of the perforated plate and the baffles.

5 Claims, 3 Drawing Figures PATENTEDJAN 1 14 SHEET 2 0F 2 1 BLOWN FILMTUBE COLLAPSING This application is a divisional of US. Pat. No.3,689,609, issued Sept. 5, 1972.

This invention relates to collapsing of a blown film tube or bubble. Italso relates to a bubble collapsing frame assembly.

In one of its concepts the invention provides a method for collapsing ablown film, tube or bubble which comprises forcing air through perforatesurfaces of collapsing frame members onto the surface of the filmbubble. In another of its concepts the invention provides a film, tube,or bubble collapsing frame comprising at least one, but preferably two,separate plenum chambers which have perforated metal surfaces facing thefilm bubble and into and through which air can be forced onto thesurfaces of the bubble to collapse the same. In a further concept of theinvention it provides Within the plenum chamber a baffle system, forexample, two baffles, which can be adjusted, as by ropes, to cause theair within the plenum chamber to emerge therefrom, largely onto thebubble.

It is known in the art to extrude a tubular film or bubble, as ofplastic, extruded from an extruder, the bubble being inflated by meansof fluid pressure conducted into a tube as it is extruded from theextruder. The hubble is then later collapsed by a collapsing frame.

Collapsing frames having various structures are known. Frames havingrollers, wire mesh, perforation or simply plates in the surfaces used tocollapse the bubble are known. For example, US. Pat. No. 3,221,370,issued Dec. 7, 1965, discusses a cooling shield with baffles beingutilized to assure uniform distribution of the heat exchange mediumtherein. German Plastics, August 1967, pages 607-618 shows in FIG. 14 aplate portion which is perforate.

It has now occurred to me to provide a collapsing frame comprising atleast one, but preferably two, or more, plenum chambers having perforatefaces adjacent the film bubble to be collapsed and to blow air throughthe perforate faces so as to cool and/or to lubricate the movement ofthe film or plastic against the face or faces of the collapsing framechamber members. In lieu of flat faced plenum chamber or chambers therecan be substituted within the scope of the several concepts of theinvention a conically shaped chamber which can be designed to be sizedby adjustment as by having plates slidably engaging and, therefore,telescoping into each other.

Further, it has occurred to me to place within such plenum chamber, asherein described,,one or more, preferably at least two, baffles topermit forcing the air out from the chamber onto the film surface in amanner as desired.

An objectof the invention is to provide a method for collapsing a blownfilm tube or bubble. Another object of the invention is to provide anapparatus or assembly for collapsing a blown film tube or bubble. It isa further object of the invention to provide a method and apparatuswhereby to adjust the egress of air from a collapsing frame so as tocause it substantially to impinge, as desired, upon a blown film tube orbubble being collapsed thereby.

Other aspects, concepts, objects and the several advantage of theinvention areapparentfrom a study of this disclosure, the drawing andthe appended claims.

According to the present invention there is provided a method forcollapsing a blown tube film which comprises passing the same into acollapsing frame and maintaining a flow of air on the surfaces of theframe and film during the collapsing thereof.

Further, according to the invention the air flow will be sufficient tolubricate the passage of the film through the collapsing frame as bymaintaining a thin film of air between the plastic film or tube and theface of the collapsing frame adjacent to the film.

Thus, according to the method of the invention there is provided atleast one plenum zone into and through and out of which air is blownonto the film being collapsed. Still further according to the inventionthere is provided a blown film tube collapsing frame assembly comprisinga plenum chamber disposed to cause collapsing of a tube passing adjacentthereto, a perforate face in said chamber adjacent said tube and airinlet means into said plenum chamber.

Further according to the invention there is provided within the plenumchamber an adjustable baffie system so constructed in range that the airflow in and from said chamber through the perforate phase is directedprimarily onto the surface of the tube being collapsed.

In one embodiment there are at least two baffles provided within thechamber and the chamber is composed of at least two plates or faceswhich sealingly engaged the baffles while the baffles are, nevertheless,slidably retained between said plates.

A magnet or magnets can be imbedded in the baffles to cause the plates,particularly the perforate plate, of the plenum chamber to adhere to thebaffles so as to form a chamber of a desired size and shape within theoverall plenum chamber as will be more evident when viewing the drawingand its description.

Further, ropes can be attached to the baffles, also as shown anddescribed in connection with the drawing, so that the baffles can beadjusted. from outside of the plenum chamber.

As a feature of the invention, there are provided elements within theplenum chamber for pivotably engag ing at least one of the ends of thebaffles while at the other end pivotably and slidably with respect tothe pivots engaging the other ends of thebaffles by angularlyconstructed retaining elements which at all times form a seal againstundue air flow from within the baffles except through the perforationsin the perforate face of the plenum chamber. 1

The use ofa myriad of air jets forming an air film be tween the tube orplastic film surface and the collapsing frame aids to lubricate thepassage of the plastic tube being collapsed through the collapsing frameand thus importantly aids to eliminate wrinkles which frequently form atthe collapsing frame during the extrusion and flattening of blown film.The frame of the invention can be used on any blown line but isespecially useful with those plastic which readily tend to presentmechanical or other problems such as wrinkling. In the drawing,

FIG. 1 is an isometric view of the general operation of blowing a filmshowing the general positioning of the plenum chamber or chambersconstituting the collapsing members of the invention.

FIG. 2 is a vertical face view of one of the collapsing frame plenumchamber members with the perforate face or front cover removed so that.the inside workings .of the baffle members can be seen and described.

FIG. 3 is a vertical view from the end of the frame member incross-section at the air or cooling medium inlets as more fullydescribed now.

Referring now to FIG. 1, tubular film issues from an extruder through aring die and extends upwardly between a pair of plenum chambers l. Theplenum chambers l are positioned so that the film tube is collapsedwithout wrinkles before it enters the nip rolls.

Referring to FIG. 2 of the drawings, 2 is a portion of the plenumchamber making up the back plate or closure of the plenum chamber. Airinlets 3 and 4 supply air into the chamber. The chambers are equippedwith movable or adjustable baffle members 5 and 6 pivotably hinged attheir upper ends at 7 and 8. At their lower ends the baffles arepivotably and slidably engaged in slots 9 and 10 cut into slidablyadjustable members 11 and 12 which are mounted in channel 13. Pieces 11and 12 act to extend the baffles to the bottom of the chamber to avoidloss of air between the baffle bottoms and the chamber bottom. Ropespassing over pulleys 14, 15, 16 and 17, as shown, and attached andfixed, also as shown, are adapted in the assembly to permit adjustingthe positions of the top and bottom ends of the respective baffles. Asshown at the upper ends, baffles 5 and 6 are slotted to permit therespective ropes to pass therethrough.

The upper ends of the baffles are attached to slidable members or hangerbrackets 18 and 19 which are slidably retained in channel 20.

At the lower ends the pivots 2] and 22 of the baffles are biased againstthe slot walls by leaf springs 23 and 24. These flat leaves also act toseal against air loss between the baffle bottom ends and the pieces 11and 12.

In the embodiment described the baffles are equipped with magnets 25 and26 imbedded into the surfaces of the baffles to ensure closure contactof the front wall of the plenum chamber and the baffles.

Referring now to FIG. 3, the front cover 30 is perforate at 31. Airenters via 3 and 4 and is spread between baffles 5 and 6 by means ofbaffle plates 32 and 33 which are held in position by struts 34, 35 and36, 37, respectively. Baffle plates 32 and 33 can be shaped and sopositioned as to ensure a desired flow distribution of air into theplenum chamber to between the baffles 5 and 6.

As evident from the drawing, the ropes extendto without the plenumchamber at both sides thereof. There are two ropes attached to each endof each baffle so that each end of the baffle can be moved or slid fromor toward its respective end of the plenum chamber.

Reasonable variation and modification are possible within the scope ofthe foregoing disclosure, the drawing and the appended claims to theinvention the essence of which is that there has been provided a methodfor collapsing a blown tube film by passing the same into a collapsingframe and there maintaining a flow of air on the surfaces of the frameand film during the collapsing thereof and that an apparatus or assemblycomprising a plenum chamber disposed to cause collapsing of a tubepassing adjacent thereto has been provided, the chamber having aperforate face and means within the chamber to supply air from withinthe chamber into and through the perforate face onto the tube beingcollapsed; in the now preferred embodiment the plenum chamber comprisingadjustable baffles so as to be able to adjust the effective face of theplenum chamber facing the tube being collapsed to put substantially allthe air onto said tube from said chamber.

I claim:

1. In a blown film tube collapsing frame assembly including means forcollapsing a blown tube and means for conveying said tube into andthrough said collapsing means, said assembly comprising also a plenumchamber disposed to cause collapsing ofa tube passing adjacent thereto,a perforate face in said chamber adjacent said tube and air inlet meansinto said plenum chamber, an adjustable baffle system so constructed andarranged as to be able therewith to adjust the effective face of theplenum chamber facing the tube being collapsed so that the air flow inand from said chamber through the perforate face is directed primarilyonto the surface of the tube.

2. An assembly according to claim 1 wherein at least two baffles areprovided within the chamber, the chamber is composed of at least twoplates or faces, the plates substantially sealingly engage the bafflesand the baffles are slidably retained between said plates.

3. An assembly according to claim 2 wherein at least one magnet isprovided in the baffle to attract to the baffle the perforate plate orface of the plenum chamber.

4. In a blown film tube collapsing frame assembly including means forcollapsing a blown tube and means for conveying said tube into andthrough said collapsing means, said assembly comprising also a plenumchamber disposed to cause collapsing of a tube passing adjacent thereto,a perforate face in said chamber adjacent said tube and air inlet meansinto said plenum chamber; an adjustable baffle system so constructed andarranged as to be able therewith to adjust the effective face of theplenum chamber facing the tube being collapsed so that the air flow inand from said chamber through the perforate face is directed primarilyonto the surface of the tube, wherein at least two baffles are providedwithin the chamber, the chamber is composed of at least two plates orfaces, the plates substantially sealingly engage the baffles and thebaffles are slidably retained between said plates and wherein ropes areattached to at least one of the top and bottom ends of the baffles, theropes extend to without the chamber from each side of each of saidbaffles and can be used to pull the baffles in said chamber eithertoward or away from each other at at least one of their top ends andtheir bottom ends.

5. An assembly according to claim 4 wherein the top ends of the bafflesare pivotably engaged, each of them in a slidable hanger and the bottomends of the baffles are pivotably engaged by pivots each of them engagedin a slotted slidable member, the slotted slidable members being soconstructed and arranged as to be in extension of the baffles so as topermit motion of the baffles without allowing air substantially toescape from between the baffles.

1. In a blown film tube collapsing frame assembly including means forcollapsing a blown tube and means for conveying said tube into andthrough said collapsing means, said assembly comprising also a plenumchamber disposed to cause collapsing of a tube passing adjacent thereto,a perforate face in said chamber adjacent said tube and air inlet meansinto said plenum chamber, an adjustable baffle system so constructed andarranged as to be able therewith to adjust the effective face of theplenum chamber facing the tube being collapsed so that the air flow inand from said chamber through the perforate face is directed Primarilyonto the surface of the tube.
 2. An assembly according to claim 1wherein at least two baffles are provided within the chamber, thechamber is composed of at least two plates or faces, the platessubstantially sealingly engage the baffles and the baffles are slidablyretained between said plates.
 3. An assembly according to claim 2wherein at least one magnet is provided in the baffle to attract to thebaffle the perforate plate or face of the plenum chamber.
 4. In a blownfilm tube collapsing frame assembly including means for collapsing ablown tube and means for conveying said tube into and through saidcollapsing means, said assembly comprising also a plenum chamberdisposed to cause collapsing of a tube passing adjacent thereto, aperforate face in said chamber adjacent said tube and air inlet meansinto said plenum chamber; an adjustable baffle system so constructed andarranged as to be able therewith to adjust the effective face of theplenum chamber facing the tube being collapsed so that the air flow inand from said chamber through the perforate face is directed primarilyonto the surface of the tube, wherein at least two baffles are providedwithin the chamber, the chamber is composed of at least two plates orfaces, the plates substantially sealingly engage the baffles and thebaffles are slidably retained between said plates and wherein ropes areattached to at least one of the top and bottom ends of the baffles, theropes extend to without the chamber from each side of each of saidbaffles and can be used to pull the baffles in said chamber eithertoward or away from each other at at least one of their top ends andtheir bottom ends.
 5. An assembly according to claim 4 wherein the topends of the baffles are pivotably engaged, each of them in a slidablehanger and the bottom ends of the baffles are pivotably engaged bypivots each of them engaged in a slotted slidable member, the slottedslidable members being so constructed and arranged as to be in extensionof the baffles so as to permit motion of the baffles without allowingair substantially to escape from between the baffles.